To @Gordon's list of things to check: What about the power stability? Some com modules tend to have at some times very high power demands. What is the stability of the power rails / connectivity?
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
To @Gordon's list of things to check: What about the power stability? Some com modules tend to have at some times very high power demands. What is the stability of the power rails / connectivity?